Damped spring means



March 5, 1968 R. l.. CARLSON DAMPED SPRING MEANS Filed March 24 1966United States Patent Gte 3,371,442 Patented Mar. 5, 1968 3,371,442DAMPED SPRING MEANS Robert L. Carlson, Chicago, Ill., assignor to W. H.Miner, Inc., Chicago, Ill., a corporation of Delaware Filed Mar. 24,1966, Ser. No. 537,206 3 Claims. (Cl. 42-74) ABSTRACT F THE DISCLOSURE Anormally extended damped spring operably connected between therelatively movable stock and buttstock boot of a shotgun or the like toabsorb and dissipate the shock of recoil with the damped spring having aclosed chamber filled with a compressible solid fixed to one of therelatively movable members and a piston rod iixed to the other andhavin-g a piston provided with orice means disposed in the closedchamber, the compressible solid providing a damping and spring force onthe piston as the rod moves into the chamber and reduces the volume ofthe compressible solid while forcing same through the orifice means withthe expansion of the compressible solid after each recoil serving as thesole force for returning the damped spring to its normally extendedcondition.

My present invention relates generally to damped springs means and moreparticularly to damped spring means adapted to be incorporated inShotguns, rifles and the like for absorbing recoil shock forces.

As is well kno-wn, when a firearm, such as a shotgun or ritie isdischarged, the energy released in igniting the cartridge not only sendsthe bullet out of the barrel but also drives the gun sharply rearward.This recoil thrust passes through the gun and slams into the shootersshoulder and cheek, often causing injury or discomfort to the shooter.Prior eorts to absorb recoil shock have consisted of providing the buttend of the gun with rubber pads or spring arrangements. These devicesyhave often resulted in clumsy stock structures and have not proved veryeffective. Most recently, hydraulic shock absorber arrangements havebeen installed inside the gun stock. In the main, such devices arecomplex in design, are diicult to seal, and require constantmaintenance.

It is an object of my present invention t0 provide damped spring meansbetween the :gun stock and a relatively movable buttstock boot forabsorbing recoil forces. In general, damped spring means comprisescasing means with a primary chamber therein, a piston rod extendingoutwardly of the primary chamber for receiving shock forces, and apiston at the end of the piston rod within the primary chamber. Thepiston provides axial orifice means, and the primary chamber is filledwith a compressible solid. Preferably, the casing means is secured tothe buttstock boot and the piston rod is secured to the gun stock. Asthe piston rod moves into the primary chamber in response to recoilforces, the reduction in volume of the compressible solid, and thethrottling effect produced by the compressible solid being forcedthrough the orice means, impose a damping and spring force on the pistonrod and piston. Damped spring means of this type are easily sealed andrequire minimum maintenance.

It is another object of my present invention to provide a firearmconstruction, as described, wherein the buttstock boot slidably receivesthe gun stock and serves to enclose the damped spring means.

It is a further object of my present invention to provide damped springmeans which is compact in construction and relatively simple in design.In this connection, the damped spring means of my present inventionpreferably has an elongated body portion of generally oblong crosssection with the axis of the primary chamber coinciding with thelongitudinal axis of the casing. Additionally, the primary chambercommunicates with an auxiliary chamber which is lgenerally C-shaped inconfiguration. The leg portions of the auxiliary chamber are arranged onopposite sides of the prim-,ary chamber and the axes thereof lie in theplane of the major cross sectional axis of the casing. Thus, for a givensize of damped spring means, optimum damping and spring characteristicsare alorded.

It is a still further object of my present invention to provide dampedspring means, as described, which includes means for varying the initialpressure of the compressible solid in the primary and auxiliarychambers.

Now in order to acquaint those iskilled in the art with the manner ofconstructing and using devices in accordance with the principles of mypresent invention, I shall describe in connection with the accompanyingdrawing a preferred embodiment of my invention.

In the drawing:

FIGURE l is a view, partly in elevation and partly in section, of a gunstock, a relatively movable buttstock boot and damped spring means,arranged in accordance with the principles of my present invention;

FIGURE 2 is a vertical longitudinal median sectional view, on anenlarged scale, of the damped spring means of my present invention;

FIG-URE 3 is an elevational view of one end of the damped spring meansof FIGURE 2; and

FIGURE 4 is a sectional view, taken substantially along the line 4 4 inFIGURE 2., looking in the direction indicated by the arrows.

Referring now to FIGURE 1, the stock of a shotgun is designatedgenerally by the reference numeral 10. The gun stock 10 has an internalrecess or cavity 12 opening rearwardly thereof. The recess 12 is adaptedto house a recoil shock absorbing damped spring unit which incorporatesthe principles of my present invention and which is indicated generallyby the reference numeral 14. The construction, mounting and operation ofthe damped spring unit 14 will be described in detail hereinafter. Itwill be appreciated that the unit 14 is shown incorporated in a shotgunfor illustrative purposes only and that the principles of my presentinvention can be used with any firearm which is tired from the shoulder.

As shown in FIGURES 2, 3 and 4, the recoil shock absorbing clampedSpring unit 14 includes a casing 1b comprised of an elongated bodyportion 18 of generally oblong or tiattened cross section, a forwardwall 20 and a rear wall 22. Viewing FIGURE 4, the dot A indicates thelongitudinal 'axis of the body portion 18, an imaginary horizontal linepassing through the longitudinal axis corresponds to the minor crosssectional axis, and an imaginary vertical line passing through thelongitudinal axis corresponds to the major cross sectional axis.

Projecting inwardly from the forward casing wall 20 are innerlongitudinal web portions 24 and 26 which terminate short of the rearwall 22. The web portions 24 and 26 serve to define with the otherportions of the casing 16 and inner cylindrical primary chamber B and anauxiliary generally C-shaped chamber C. The axis of the primary chamberB coincides with the longitudinal axis A of the casing 16, and the legportions of the auxiliary chamber C are arranged on opposed sides of theprimary chamber B with the axes thereof lying in the plane of the majorcross sectional axis of the casing 16.

The forward casing wall 20 is formed with an opening 28 which is coaxialof the longitudinal casing axis A, and an inwardly facing annularshoulder 30 is defined at the inner end of the opening 28. Extendingthrough the opening 28 and projecting into the chamber B is a piston rod32. The piston rod 32, intermediate of its ends, is formed with a collarportion 34 that is engageable with the casing 3 shoulder 30 'to limitmovement of the piston rod 32 out- =wardly of the casing 16. The pistonrod 32 is also provided, at its inner end, with a piston 36. Theperiphery of the piston 36 is spaced from the interior cylindricalsurface of the chamber B to dene therewith axial orifice means in theform of an annular orifice. Additionally, the inter-communicatingchambers B and C are filled with a compressible solid or elastomer 38such as silicone rubber. To prevent the escape of compressible solidpast the piston rod 32, an annular seal 40 is mounted in the forwardwall20.

To permit the admission of compressible solid into the casing 16, ailler plug 42 is provided in the rear wall 22. Additionally, a screw 44is threaded through the forward casing wall 20 for effecting preloadingof the cornpressible solid 38. As the screw 44 is threaded axiallyinwardly or outwardly, the initial pressure of the compressible solid isvaried due to the change in the effective volume ofthe chambers B and C.

The casing 16 is slidably mounted within a sleeve member 46 having aforward end wall 4S. The forward end of the piston rod 32 is suitablysecured, as by a threaded connection, to the forward end wall 48. Thesleeve 46 and the forward end wall 48 thereof are ixedly mounted in aconventional manner within the recess 12 of the gun stock 10. Duringmovement of the gun stock l relative to the casing `16, correspondingmovement is imparted to the piston rod 32 while the sleeve member 46slidably guides the casing 16.

As is evident from FIGURE l, the rear portion of the casing 16 projectsrearwardly out of the gun stock 10. To 'house the above-mentionedprojecting portion of the casing 16, and also to provide a cheekprotector, a buttstock boot 50 is provided for the gun. The buttstockboot 50 comprises a housing 52, a spacer 54, and a butt plate 56. Thehousing 52, which is preferably fabricated of a plastic material, is inthe shape of a conventional buttstoclc boot and is arranged to slidablyengage the rear portion of the gun stock that extends into the housing.The spacer 54 is of the same material as the housing 52 and providesadditional cushioning means for the shoulder of the gunner. The spacer54 is secured to the rear casing wall 22 by means of bolts 58, and bearsagainst shoulders 59 and 60 formed in the housing 52. The butt plate 56,also of a plastic material, is adapted to t over the rear end of thehousing 52 and is removably snapped into position.

I shall now describe the operation of my recoil shock absorbingmechanism which is shown at rest in the drawing. When `the gun is fired,the gun stock 1t) is urged rearwardly and telescopes into the housing52. This telescoping yaction moves the piston rod 32 and piston 36rearwardly within the primary chamber B. During such movement, thevolume of chamber B is reduced to the extent of displacement by thepiston rod 32, thus increasing the pressure of the compressible solid 38in both chambers B and C. Concurrently, the compressible solid 38 isforced through the annular orice surrounding the piston 36 therebyproducing a throttling effect. The described volume-pressure change ofthe compressible solid, and the attendant throttling effect, impose adamping and spring force on the piston and piston rod, and thereby serveto dissipate the energy of the recoil shock force resulting from firingof the gun. The damped spring unit 14 will absorb up to 90 percent ofthe recoil force.

When the recoil shock force is fully dissipated, the pressure of thecompressible solid 38, acting on the unbalanced area of the piston rod32 within the chamber B, causes the piston 36 and piston rod 32 toyreturn to the position shown in FIGURE 2. During the return stroke ofthe piston rod 32, the compressible solid flows back through the annularorice -surrounding the piston 36 to lill the space being vacated by thelatter. Correspondingly, the pressure of the compressible solid 38returns to the normal preload pressure'. In this connection, engagementofthe piston rod collar portion 34 with the casing shoulder 39 serves toestablish the rest position of the piston rod 32. Finally, by reason ofthe arrangement of the chambers B and C in a common plane, desirabledamping and spring characteristics are afforded in a compactconstruction. k Y

While I have shown and described what I believe to be a preferredembodiment of my present invention, it will be understood by thoseskilled in the art that various rearrangements and modifications may -bemade therein without departing from the spirit and scope of myinvention.

I claim:

1. A gun stock and a relatively movable buttstock boot at the rear endthereof, a normally extended damped spring means acting between Said gunstock and said buttstock boot for dissipating the energy of recoilforces imposed on said gun stock, said normally extended damped springmeans comprising a casing secured to said buttstock boot and having aprimary chamber therein, a piston rod extending outwardly of saidchamber and connected to said gun stock, a piston at the end of saidpiston rod within said chamber and providing axial orifice means, and acompressible solid lling said chamber for providing a damping and springforce on said piston rod and said piston as said piston rod moves intosaid chamber and reduces the volume of said compressible solid while thelatter is forced through said orice means, said compressible solidexpanding after each recoil and serving as the sole force for returningsaid damped spring means to its normally extended condition, andadjustable means for varying the initial pressure of said compressiblesolid.

2. The device of claim 1 wherein said primary charnber is cylindricaland wherein an auxiliary chamber is provided in said casing incommunication with said primary chamber whereby to accommodate a greatervolume of said compressible solid.

3. The device of claim 1 wherein said casing is provided with shouldermeans adjacent one end of said pri-- mary chamber, and said piston rodistprovided with a collar portion that is engageable with said Shouldermeans for limiting outward movement of said piston rod relative to saidcasing.

References Cited UNITED STATES PATENTS 2,668,049 2/l954 Taylor 267-63 XR2,846,211 8/1958 Taylor 267-63 2,994,524 8/1961 Jarret et al. 267-13,152,798 10/1964 Iarret et al. 267-1 837,601 12/1906 Behr 42-742,731,753 l/ 1956 Mathieu 42-74 3,001,312 9/1961 Campbell 42-743,176,424 4/1965 Hoge 42-74 3,209,482 10/1965 Kuzma et al 42-743,300,889 1/l967 Baker 42-74 BENJAMIN A. BORCHELT, Priltary Examiner.

T. H. WEBB, Assistant Examiner.

